M=10**9+7;F=[1];P=[0]
pow=->a,n=M-2{a.pow(n,M)}
N,K=gets.split.map &:to_i
1.upto(K+1){|i|P<<(pow[i,K]+P[-1])%M;F<<i*F[-1]%M}
N<=K+1&&(p P[N];exit)
N%=M
r=0;a=1
0.upto(K+1){|i|a=a*(N-i)%M}
0.upto(K+1){|i|
v=P[i]*a%M*pow[N-i]%M;
w=F[K+1-i]*F[i]%M;
v=v*pow[w]%M;
r=(r+(i%2!=-~K%2 ? -v : +v))%M
}
p r